Former President Ford was admitted to the Mayo Clinic on Tuesday for "testing and evaluation," his office said in a statement, though little else was disclosed about the hospital stay.
The statement gave no details about why the 93-year-old former chief executive went to the clinic about 75 miles southeast of Minneapolis, and Mayo offered no additional details.
"No further releases or updates are anticipated prior to early next week," said the statement issued from Ford's office in Beaver Creek, Colo. Ford also has a home in Rancho Mirage, Calif.
Mayo Clinic spokesman John Murphy confirmed that Ford was admitted but said he had no further information and anticipated no other announcements from Ford's family or the clinic on Tuesday.
A message seeking comment from Ford's chief of staff, Penny Circle, was not immediately returned.
A California friend, Lee Simmons, said he heard in the last two days that Ford was planning to undergo a series of tests for various "medical problems." He didn't have details but said he believed the tests had been planned in advance.
"He does have some medical problems ... I did hear that they want to do a series of tests to make sure he's OK and improve his quality of life," Simmons, of Palm Desert, said in a telephone interview.
Simmons said he visited Ford last week at the former president's vacation home in Beaver Creek.
"I just saw him and he was doing fine. He's talking, his mind is sharp ... he's eating, talking to his family," Simmons said.
Last month, Ford spent a few days in Colorado's Vail Valley Medical Center because of shortness of breath. In January, he was hospitalized for 12 days in Rancho Mirage for treatment of pneumonia.
Ford suffered two small strokes five years ago and spent about a week in a hospital.
He became the nation's oldest living former president after the death of Ronald Reagan in 2004.
Ford was House minority leader when President Nixon chose him to replace the resigned Spiro Agnew as vice president in 1973. Ford became president on Aug. 9, 1974, when Nixon resigned amid the Watergate scandal.